Diorganotin(IV) Complexes of Organoselenolato Ligands with Pyrazole Moieties-Synthesis, Structure and Properties.

Diorganotin(IV) compounds of types RR'Sn(SeCH2CH2pz)2 [R = R' = nBu (2), Ph (3); R = 2-(Me2NCH2)C6H4, R' = Me (4), nBu (5), Ph (6)], and RR'SnX(SeCH2CH2pz) [R = 2-(Me2NCH2)C6H4, R' = nBu, X = Cl (7), R' = Me, X = SCN (9)], as well as [2-(Me2NCH2)C6H4](Me)Sn(NCS)2 (8), and the tin(II) Sn(SeCH2CH2pz)2 (10) (pz = pyrazole), were prepared by salt metathesis reactions between the appropriate diorganotin(IV) dichloride or dipseudohalide and Na[SeCH2CH2pz], with the latter freshly prepared from (pzCH2CH2)2Se2 (1). The solution behaviour of these compounds was investigated by multinuclear NMR (1H, 13C, 77Se, 119Sn), and the NMR spectra showed the existence of the Se-Sn bonds in solution. Compounds 4 and 5 showed decomposition in a solution of chlorinated solvents with the formation of selenium bridged dimeric species of type {[2-(Me2NCH2)C6H4](R')Se}2 [R' = Me (4-a), nBu (5-a)], as the single-crystal X-ray diffraction studies revealed, in contrast with compound 9, for which a monomeric structure was observed with the desired composition. The solid state structures of 4-a, 5-a, 8, and 9 revealed N→Sn intramolecular coordination of the nitrogen atom in the pendant CH2NMe2 arm. The NMR spectra suggested such a coordination at room temperature only for compound 7.